Some comments on S30V (stainless CPM-3V) by Phil Wilson

[Cliff Stamp]

This came up when I was discussing some details of heat treating and microstructure with Phil Wilson awhile back. He has been using some S30V blades and the results have been impressive. He can bend one of his fillet blades to 90 degrees without fracture. That is pretty decent for a ~60 RC stainless steel, however you have to consider the thin stock and distal taper, that is not going to fly with a 1/4" sabre ground "tactical".

Some comments on the heat treating and finish :

Very nice to heat treat . Easy to get 61 (seems to be the best hardness to use) with 1970 austentizing and 400 temper. With an air quench. I haven't tried oil quench yet . With 2000 quench I can pick up about 1 pt hardness with Sub Zero with a final as quenched of 63. AT 1950 no apparent increase in hardness out of the LN2. Grinds in the hardened state a little easier than S-60V. A dream compared to 90V or 10V. Difficult to get a good 400-600 grit belt finish. I just hand rub them to a satin finish from 240 grit and again takes about half the time as S-90V. Steel cost is more than 154CM but about half of S-90V. Good corrosion resistance. Can cut up a grapefruit and leave the knife on the board overnight and no corrosion evident, but the blade is duller. Same as 90V in that regard. It seems to be tougher than 154CM , but probably not at the A2 category . It is the best stainless I have worked with so far for toughness. (based on one Fillet knife and one semi) Edge holding is a little letter better than S60V at R 57, but not in the S-90V or 10V category-- to be expected not a surprise here.

Seems to be pretty much what you would expect, doesn't offer anything of interest for me personally. I'd just go with one of Phil's S90V knives at 62-63RC for a high performance light cutting blade and 3V for a heavy use blade where a high level of wear resistance was desired and something like 5160 / L6 / S7 where it wasn't.

-Cliff

 

[Will York]

Cliff-

Thanks for passing those remarks along. I'm a little disappointed that Phil doesn't think S30V measures up to A2 in toughness, although I suppose this shouldn't be a surprise. But A2 toughness in a thinly-beveled edge, such as on the Reeve's Project One you tested, didn't seem all that impressive to me. As I recall, that A2 blade had micro-chips all along its edge after heavy use, while a mod-INFI #7 edge showed no such damage. And INFI is fairly rust resistant to begin with, which is one area of apparent advantage over 3V so far. Your thoughts?

-Will

 

[Cliff Stamp]

Reeves runs his A2 fairly soft and doesn't do a full cryo treatment on the blade, that is not exactly a recipe for maximum performance. A2 is an air hardening steel that is designed to run at ~60 RC where it has its optimum toughness of about 41 ft.lbs (c-notch). If you drop the RC down to 58, the toughness goes down to 29 ft.lbs. In general you are better off switching steels than underhardening. A6 for example would give a maximum toughness of about 67 ft.lbs at about 55 RC which is where Reeves hardens his A2.

In regards to his comments about toughness, first off I am sure Phil would caution because he is only reporting on a couple of blades, he would obviously want more work before he would stand on a firm statement. However in general, I put a lot behind what Phil has to say about strength and toughness and other properties because of the way he grinds his blades and the fact that he will take them to failure, usually just edge as that is all he is interested in.

His edges are both very thin and acute and thus he can detect very small differences in strength and toughness which you would never see in an overbuilt blade. When I asked about the edge durability of 10V he described some work that chipped the edge, when I asked about the durability of 3V he described some work that blew a piece out of a bowie class blade. As well I have duplicated pretty much everything he has described to me anyway with his 10V and S90 V blades.

In regards to A2 in general, it is only really considered a tough steel if you compare it to the stainless steels, or the steels optomized for wear resistance like D2 / M2 etc. . A2 is far more brittle than like 5160, L6 etc., let alone the shock steels like S7. Then again A2 has a much greater wear resistance than those steels, which is no surprise as an increase in one tends to cause a decrease in the other.

In regards to corrosion resistance, I have never had a problem with it on heavy use blades. I have left them uncleaned after use for weeks with only minor spotting. They will however not stand up to extended exposure to food acids, blood etc., nor long term soaks in salt water (days), but these are not personal common uses. For blades that would see those kind of conditions I would want either a light hunter or fillet knife, and I would go with S90V for both of these.

For people however who like the performance of ATS-34 / 154CM, it would seem like S30V would be well welcomed. The properties should allow edge refinement and thus an increase in cutting ability without a loss of durabilty and an increase in edge retention.

-Cliff

 

[Will York]

Thanks, Cliff. Obviously, as Jerry Hossom has said, "it's not 3V".

It will be interesting to see how it stacks up to 154CM/ATS34, though, and to see how much tougher it is than S90V as well.

-Will

 

[Don Powell]

The subject of toughness at certain HRC is very interesting.
It appears that the effort to increase toughness by reducing
hardness, often has the opposite effect as per the reference
to A2. The crucible book would suggest that A2 at HRC 60 is
much tougher than at lower hardness. Phil Wilson seems to heat
treat to a higher hardness for most things, but is HRC 62- 63
for S90V a typo?

 

[Cliff Stamp]

Will, it would seem to be a very good choice for production companies who want to step up from ATS-34, but don't want to see the price increase that S90V would induce. Plus the low impact toughness of S90V means that in general, for production knives, you have to run it fairly soft and this really undercuts its abilities. The higher durability of S30V would mean that it could be run harder or with a more acute geometry, or maybe both.

Don, yes toughness is not nearly as trivial as make it softer and it gets tougher, there are issues with grain size and carbide formation, plus as well strength plays a large part in impact toughness. A very weak and ductile steel can have a low impact notch impact toughness because it gives away too much strength. The optimum RC is one that allows a very high strength without inducing too brittle a nature to the steel.

In regards to the high RC for S90V, yes I thought that was a typo when I first read it as well. He was running them softer about 2 years ago, down to 59RC. His 10V blades were then about 62 RC. Now everything seems to have jumped up a few points. He is experimenting is all, and not resting on blade performance. Note these are very task specific blades for experienced users and thus he can run them much thinner and harder than production knives, an excellent example of the benefits of going custom.

-Cliff

 

[Jerry Hossom]

To begin with, I'll state unequivocally that A2 is a tough steel, used in many circumstances where toughness is needed. It's not as tough as 3V, but tough enough that Mario took a shaving sharp A2 sword blade at Rc58 through a shank of beef, including 3-1/2" of bone in one pass without chipping the edge. It did flatten a spot, but that is plastic deformation and not breaking. Many tactical knifemakers use A2 as the only acceptable alternative to 3V. So if S30V measures up to A2 it is a most worthy steel, offering high levels of all three desireable qualities - impact toughness, wear resistance, and corrosion resistance.

While Crucible certainly did price it to sell, and they should be applauded for that, it will not make inexpensive knives due to the higher cost of finishing. Post hardening, I agree with Phil that it is not bad up to about 320 grit, but beyond that it hangs onto scratches like it owns them. The two blades I've finished were taken to 800 grit before brushing them out with 600 grit compound on a loose buff (about the same as 800 grit by hand). Each took me a full day, compared with about half that for 3V. It's quite possible this steel will put me in the bead blasting business for the first time.

I should have some test results in a week or two. Preliminary testing (unpublished) at Crucible on pilot lots indicated transverse toughness was virtually the same as A2, and 3-4 times that of ATS-34/154CM.

I disagree with the notion that it might not offer a meaningful alternative to what's available. The substantially improved toughness over current stainless steels will allow it to be used in a host of demanding applications where stainless is desireable. Toughness means a knife can be made lighter and easier to use. It's wear resistance should be better than most people will be able to use. I already have customers who can dress and skin 7-8 deer with 154CM without sharpening, so I reckon they can do a whole herd with S30V, certainly sufficient for most. Of paramount interest to some, is its potential for use in tactical knives where combat conditions make stainless a desireable quality and toughness is a must. Gaining toughness with the steel means reducing weight for the same level of durability in the knife.

I will point out, however, that the merits of this steel will not be clearly understood until a lot more work is done with it. A couple knives are not able to accurately define the best way(s) to use the steel and how to get the most from it. That will take some time, and a whole lot of steel dust before we can say, here's what it is and here's what it does and here's how you make it do that. One thing is certain though, it will be better than what some people are now using, especially factories. If you just think about it for a little bit, a 3-4X improvement in toughness over ATS-34 makes for a very attractive choice in knife blades.

 

[Cliff Stamp]

Jerry Hossom :

[A2]

It's not as tough as 3V, but tough enough that Mario took a shaving sharp A2 sword blade at Rc58 through a shank of beef, including 3-1/2" of bone in one pass without chipping the edge.

That doesn't demonstrate any significant toughness assuming Mario is of considerable skill and can perform the cut in a very controlled manner, which based on what I have read, is quite obvious. I would assume the cut is done in a very fluid manner with a bare minimum of twisting, and no forced torquing. Of course the edge profile is critical, from memory I recall you noting they were convex with an approx 22 degree or so edge profile. This is about 50% more obtuse than the edge on a felling axe, so it is no surprise that the profile has an inherent high level of edge durability.

If you wanted to demonstrate edge durability on bone contacts, have a cut made through a heavily weighted piece of bone that was moving at a vector that is not parallel to the direction of the cut. If the bone is stationary or moving along the cut path, then it won't exert any significant amount of stress on the blade except as a direct compression. As long as the blade is hard enough, then this won't pose much of a problem, this is why you can easily cut through nails with cheap kitcken knives if you vice them through it. It is why I could press a number stainless knives (VG-10, ATS-34) through mild steel rod, but when pounding them through they fractured. A simple carbon steel (1095), can easily handle the pounding without harm.

It is also why Mario was able to do the same thing with ATS-34 blades. It showcases his skill more than anything else. Now if Mario had chipped out a number of your ATS-34 blades on similar class bone, but the A2 one of a similar profile was unscathed then you would have an argument that the A2 was functionally tougher. Or if at the level that the ATS-34 blades chipped out on the bone, you could grind a thinner edge profile with A2 before the same thing happened. The critical part being that one blade should be getting damaged and the other not. If neither get damaged you can't really say anything concrete about durability even if the profile on one is slimmer. However the only heavily damaged blade that I recall was on an A2 blade. He used two A2 blades from the same maker, one which dented and the other which chipped. This could simply however indicate a greater control on the ATS-34 blades due to handle issues or blade profile. Or it could be rooted in the the difference in edge geometry.

Demonstrating toughness by use, isn't trivial because of the influence of skill as noted. A lot of blade issues come into play as well to further complicate matters. A knife with a better handle for example will allow a much greater control and can in effect make the edge much "tougher", not to mention of course actual changes in blade profiles. For example I damaged a few blades last winter while chopping hard knotty woods. During the summer I spent a lot of time refining my technique, and on the same blades I saw no more evidence of damage even picking the worst of the hardest wood I could find. Now I still have to factor out the effect of the winter cold, which could easily be a significant as it will make the steels more brittle. But I think the major problem I saw last winter was a lack of control during the cutting which greatly amplified the forces that the blade recieved.

Many tactical knifemakers use A2 as the only acceptable alternative to 3V.

Trends don't show much of anything except popularity. While they can be rooted in fact there is no direct correlation simply because of existance. As well it is hardly the case that the knife industry has uniform opinions on such matters. For example on a thread in the shop talk forum awhile back someone asked about D2 in a heavy use knife. The range of answers spanned the entire spectrum ranging from it is an excellent steel for such a knife, from the perspective that it is a poor choice because it is too brittle. All opinions were from very well known and respected knifemakers.

My take on A2 is pretty much what Tom Johanning noted when I asked him why he used A8, because A2 isn't tough enough for a tactical knife. Obviously this is a personal judgement based on the level of performance you feel is acceptable, there are lots of people for example who feel that AUS6 at ~55 RC has excellent edge retention.

Anyway as noted in the above, A2 certainly isn't in the same class as the spring steels, let alone the shock steels for impact toughness, so there are certaintly better steels for toughness that are cheaper than 3V. 3V by the way, is hardly an extreme shock resistance steel either. While it is very tough for a steel which has its level of wear resistance, it is pretty much at the beginning to middle ground of where the high impact cutlery steels start (5160 and the above). There are cutlery steels which have more than double the shock resistance of 3V even at full hardness.

The substantially improved toughness over current stainless steels will allow it to be used in a host of demanding applications where stainless is desireable.

Obviously yes, my take was quite simply that I wouldn't use a stainless for any knife of that class anyway, as noted obviously a personal opinion as are many issue of what is functional performance even with basic issues such as cutting ability. The only blades I would use stainless in are light use knives, and for which use, unless you consider cost, S90V is directly better. As I noted in the above, for those who do like the performance of ATS-34, then yes S30V would be a welcome improvement as it is pretty much a direct upgrade. Performance / cost would be a non-trivial argument though as always.

-Cliff

 

[Jerry Hossom]

Hey, what do I know....

 

[Rob Simonich]

Guess you dont know nothing Jerry! My first S30-V blade is in cryo. Nice, snappy heat treat! I think this steel may have a very nice combiniation of wear, corrosion resistance, and toughness, but what do I know!

 

[Will York]

Originally posted by Jerry Hossom
I will point out, however, that the merits of this steel will not be clearly understood until a lot more work is done with it.

Yep. Thinking and talking can only take us so far--and so far, the thinking and talking is just making my head sore. Glad to hear Mario is soon to have the beast in hand, and that other makers are getting into action with it. If we have the likes of Jerry Hossom, Rob Simonich and Phil Wilson making knives out of it, and the likes of Mario Dominguez and Cliff Stamp lining up to test it, I'm keenly looking forward to the outcome.

-w

 

[Jerry Hossom]

Will, let me just throw in a small dose of caution. I think it's very likely we will need to play with S30V for awhile before we have all the parameters nailed down for optmizing its use. One batch through the tempering oven at one setting is unlikely to hit on the ideal combination of hardening and tempering temperatures. We'll also need to see how the steel performs at various harnesses, each of which may be achieved with different tempering schedules. Then we'll need to optimize the blade to the steel. At the moment I'm optimistic, but there's more to learn here.

I guess I'll also have to find out what more than 3-1/2" of beef bone will constitute a measure of toughness...

 

[bandaidman]

Originally posted by Jerry Hossom

I guess I'll also have to find out what more than 3-1/2" of beef bone will constitute a measure of toughness...

rocks? rebar? chevy novas?

 

[Rob Simonich]

Exactly Jerry!

 

[Will York]

Originally posted by Jerry Hossom
One batch through the tempering oven at one setting is unlikely to hit on the ideal combination of hardening and tempering temperatures. We'll also need to see how the steel performs at various harnesses, each of which may be achieved with different tempering schedules. Then we'll need to optimize the blade to the steel. At the moment I'm optimistic, but there's more to learn here.

No surprise there, pard. In fact, if we see the full range of heat treat, geometry, and applications tested definitively within the next year, I WILL be surprised. But the quest, THE QUEST! How FUN can it get?

Rob--

I hope your mention of the Nova isn't prophetic. One of Chevy's great marketing adventures was when it decided to promote the Nova in Mexico. In Spanish, "No va" means "It doesn't go."

Thanks all.

-w

 

[rdangerer]

Originally posted by Cliff Stamp
Reeves runs his A2 fairly soft and doesn't do a full cryo treatment on the blade, that is not exactly a recipe for maximum performance. A2 is an air hardening steel that is designed to run at ~60 RC where it has its optimum toughness of about 41 ft.lbs (c-notch). If you drop the RC down to 58, the toughness goes down to 29 ft.lbs. In general you are better off switching steels than underhardening. A6 for example would give a maximum toughness of about 67 ft.lbs at about 55 RC which is where Reeves hardens his A2.

Most steels tend to get tougher as you lower the hardness, as a general rule, but there are distinct exceptions, like A2 and D2.

I just thought I'd point out that A2 is a bit weird... it has a toughness "hump"... data from a Crucible Handbook on A2:

Temper@....Hardness Rc...Toughness Charpy C (ft-lbs)
400F............61................31
500F............60................41
600F............59................37
700F............58................33
800F............58................31
900F............58................29
1000F...........57................41

I.e., if CRK takes A2 down to Rc55-57, they do make the knife somewhat easier to sharpen in the field (overrated benefit IMHO), they give up some edge holding/abrasion resistance for sure, but probably get back to a localized toughness peak at Rc57 or less.

Originally posted by Cliff Stamp

In regards to A2 in general, it is only really considered a tough steel if you compare it to the stainless steels, or the steels optomized for wear resistance like D2 / M2 etc. . A2 is far more brittle than like 5160, L6 etc., let alone the shock steels like S7. Then again A2 has a much greater wear resistance than those steels, which is no surprise as an increase in one tends to cause a decrease in the other.

-Cliff

To Cliff's point, a selected few steels at their toughness peaks vs. HRC (at least per the data set in Crucible's handbook in a hardness range that might be used for knife blades). Order is in relative terms of "wear resistance, adhesive", highest wear at top:

Steel....Tufness(ft-lb).....HRC......Adhesive Wear Resistance
============================================
M4...........32.................62.........20-25
M2...........20.................62.........8-10
3V...........40.................62.........8
3V...........50.................60.........7
3V...........85.................58.........6

D2...........23.................60.........3-4
A2...........41.................60.........2-3
A6...........67.................55

L6...........68.................56-58
O1...........32.................55-57

S5...........138.................58-60
S5...........156.................56-57
S7........... 85.................59
S7...........125.................57.........1
S7...........190.................47




Hardness helps with edge retention, prevents "rolling" of an edge, but abrasive and adhesive wear resistance is only fairly correlated with hardness.

Nothing turns out to be terribly simple in terms of relationships between hardness, wear resistance, and toughness.

 

[Jerry Hossom]

Let me offer a cautionary note on using the numbers in Crucible's book, which I also have.

These numbers were not measured on steel sections that even approximate knife blades. Further, they tend to be relative only to the point Crucible is trying to make when they present them. The A2 values for instance, are based on a hardening temperature of 1775F, and only 1775F. If the steel is hardened at a different temperature the values may change profoundly. If the steel is fast quenched, as is preferred for knives and not achievable in sections over 1/4" thick, the values will be different. If the steel is cryogenically quenched, the numbers will be different. If you follow the heat treating schedule used to generate these numbers when tempering a knife blade you will not get these numbers.

If you are going to use Crucible's book to make judgements on the performance of knife blades, you are most often going to be wrong. If you make assumptions on how a knife using a particular steel, tempered in a manner you don't know and may not understand if you did, using a blade and edge geometry you've never seen, in the hands of someone(s) you don't know, made my a maker whose work you have never seen and whose works is also specifically designed for each specific user, you will likely be more wrong than you can even imagine. It's also just a little arrogant.

 

[Rob Simonich]

Jerry I agree, and something I have said before and will say again is the heat treatments recomended by the manufacturers is usually for things like bearings, dies etc, not hand held cutlery. These heat treatments may not be the best for knives. Also the charpy test is a good starting point for measuring toughness, but it dosent tell you how an edge will behave going through 3 1/2" of beef bone. Only a whack through the bone will tell you that. By the way, I took my blade to 59-60 Rc, time to go beat!

 

[ExamonLyf]

Originally posted by Jerry Hossom
Hey, what do I know....

Well Jer.., ...it was sort of silly to reference regular old US-Born-Corn-Fed bovine anatomy as a significant measure of anything !

I also think that the Nova idea is bad considering what potentially could be a very E-X-T-E-N-D-E-D warranty period.

By means of Overnight Express.., I am shipping you the entire hind quarters of a Cape Water Bufallo. This speciman was raised on hormone and anabolic steroid injections, and had 3/16ths titanium rods inserted from epiphysis to diaphysis to replace pre-existing bone marrow. Obviously "normal marrow" would deplete any credibility, so I performed these transplants myself with a Dremmel Tool to facilitate "valid" conclusions. Please make Marios's A2 speciman available for the aforementioned clinical trials.

Since Wayne Goddard is currently preparing for the rope cutting competition at the Oregon Show in April.., I will make Wayne available to be the actual "push-cutter" for this project. Also please have Rob come by to measure wind conditions, humidity, etc...and let's get if right this time!!!!

You thought you were getting out of research huh Jerry?

By the way.., I absolutely love the "Narc"!! Wow does that little guy "cut"! I killed a vampire with it Wednesday night, but given the 4" blade length (and a rather "chubby" vampire), I did have to hammer almost the entire knife into the murderous creature. Sadly, I used a framing hammer and it sort of made some ugly "marks" on the Ironwood! This is a "Warranty Issue" ~~> no?

The CPM-3V did great!! Like lots of things.., the manubrial cartilage and boney structures of your typical vampire are far over-rated!

See ya



"Hunters seek what they [WANT].., Seekers hunt what they [NEED]"

 

[Dr.Lathe]

Read read read, digest, read read, compare, think it over, read some more, look at the charts, then look at them again, check my heat treat ovens MAX temp, read some more............ THAT"S ENOUGH!!!

Now I gotta get me some and try it for myself. Stainless A2 on steroids sounds good to me. Rust free bead blast sounds like the way to go as far as finish.

Thanks Mario for putting the fire under my ASS and getting me to try something new

AND..... thanks everyone for the time and engery spent putting this information together. It's been very informative.

Neil